Standard 0-4-0 Decoder Installation Guide

[davlyn1]

I've just read this installation guide prior to converting my first loco to DCC, which just happens to be an 0-4-0 Pug (not my most treasured in case anything goes wrong). Am I missing something or do steps 17 and 22 in this installation guide put the

 

red capacitor in series with the feed from the pickup to the decoder? Shouldn't the red wire go direct to the pickup?

 

I also wouldn't wrap the decoder in insulation. If I can find the space I'll also fit it clear of the motor to reduce heat into it.

[morairamike]

Ok I've looked at the instruction guide and the RED capacitor is NOT a capacitor but a small inductor. As this is a Hornby set of instructions and the LAW says that there should be suppression circuits fitted in a small loco, they have to show it still

 

fitted.

 

Best action is to remove the yellow and red items and discard them.

 

a capacitor will not allow DC to pass through it, an inductor which is a small coil wrapped round a ferrite core will. When capacitors and an inductor are connected to

 

form a 'pie' circuit they become an effect tuned suppression circuit to stop ac signals i.e. sparks between brush and armature from causing interference

[Fishmanoz]

The standard guide says the motor is mounted connector side down, or at least it did the last time I looked which is a while ago.

 

Irrespective, it's not true, it is connector side up so you don't have to remove it. Just unsolder all the connections

 

and throw away inductors and capacitors, not needed as decoder already has suppression included. Now solder orange and grey to motor connections, red and black to pickups, as shown in the guide, and you are done. Simplest conversion there is.

[Fishmanoz]

At least for modern ones like Collector Club, older ones must be like the Guide or they wouldn't have written it that way.

[morairamike]

The early 0-4-0 motors were fitted upside down. After removing the locating clip, you take out the motor and remove all the junk, then you can put the motor back in but up the other way so the terminals are uppermost. Put some blu-tac under the motor to

 

sit in. However these are not the best of runners and the gear mesh to the worm needs careful setting. I eventually drilled a small hole in the chassis, just in front of the screw in the base between the two pairs of wheels and the gear cog and fitted a small

 

screw which can be used for fine adjustment of the mesh. This was successful on club locos 43209 and 06008 (Pullman shunter)

[davlyn1]

Thanks morairamike for clearing up the "capacitor" that should be an inductor. No problem now why it is there originally, although I wonder what effect retaining it will have on the waveform for the control; it will slow the pulse edges a little depending

 

on the value of the inductance. The tip about meshing the worm drive will be useful. I'll retain a capacitor across the motor to reduce commutator noise since it is closer than the chip in the decoder. Any extra wire length here can radiate making the capacitor

 

in the decoder less effective. The rule for suppression of EMC is to put the capacitor as close to the brushes as possible. It helps that this motor is in a can. The capacitor across the pickups has to be discarded or it will degrade the waveform.

[Rog RJ]

davlyn1 said:

Thanks morairamike for clearing up the "capacitor" that should be an inductor. No problem now why it is there originally, although I wonder what effect retaining it will have on the waveform for the control; it will slow the

pulse edges a little depending on the value of the inductance. The tip about meshing the worm drive will be useful. I'll retain a capacitor across the motor to reduce commutator noise since it is closer than the chip in the decoder. Any extra wire length here

can radiate making the capacitor in the decoder less effective. The rule for suppression of EMC is to put the capacitor as close to the brushes as possible. It helps that this motor is in a can. The capacitor across the pickups has to be discarded or it will

degrade the waveform.

You will find that some decoders from other manufacturers do not like any capacitors on the motor and will run very poorly unless you remove them. The capacitors affect the way the back emf from the motor is measured and controlled.

Fortunately, Hornby decoders don't seem to be affected by the motor capacitors at all.